Imagine suddenly, and uncontrollably, having a completely different accent. You’ve had a stroke, or surgery, or been in a traffic accident, and when you regain your ability to speak, you sound like you’re from somewhere else. Perhaps you’re from Arizona and now you sound like you’re from England. Or you’re from Australia and sound like you’re from France. Or you’re from England and you sound like you’re from China or … Italy? Poland?

Foreign accent syndrome (FAS for short) is a real thing, though it’s very rare — fewer than 200 cases diagnosed since it was first described in 1907. It may sound like it’s just a delusion or fantasy, but fewer than 10 percent of cases have a psychological basis (for example, related to schizophrenia). Nearly all of the rest are of neurological origin: They are caused by damage or impairment to a specific area of the brain. People who have foreign accent syndrome don’t think they’re from somewhere else, and their language comprehension and overall verbal skills often aren’t affected at all … except for this one thing. And nearly all of them say they’d really like to sound like they used to, but though they try, what comes out sounds like it’s from somewhere else. The reason for this can tell us quite a lot about how we speak, and how we produce and identify different accents.